High fuel efficiency and low engine emissions are key priorities when designing a vehicle powerplant. Enablers include rapidly warming the engine to the efficient operating temperature range and the catalytic converter to the light-off temperature so that undesirable exhaust gases are catalyzed rather than allowed to escape the vehicle as emissions. Current exhaust gas waste heat recovery systems are capable of capturing engine waste heat and re-circulating it to the engine or transferring it to a downstream catalytic converter.
As hybrid vehicles and highly efficient internal combustion engines become more prevalent in the market, there is a need for a new heating source to supplement residual engine heat utilized in the vehicle. For example, excess engine heat is used today to warm up the passenger compartment through a heater core. In a highly efficient internal combustion engine, there may be an inadequate supply of residual heat generated by the engine. Likewise when a hybrid vehicle is operating in a low power demand range, such as idle or city driving, the internal combustion engine may be turned off and therefore does not produce residual heat for meeting the thermal demands of the vehicle. To satisfy thermal demands, the hybrid vehicle may continue to run the internal combustion engine to produce heat when ideally the engine should be off. Hybrid vehicles may also employ a supplemental heat pump system for cabin heating when the engine is off, which drains electricity directly from the battery pack. Both options are expensive expenditures of energy.
Since hybrid vehicles typically employ smaller engines, which produce less heat and are usually not allowed to idle, engine warm-up time may be longer compared to conventional vehicles. A supplemental heating system may be used to accelerate engine warm-up thus contributing to improved efficiency and emissions. Hybrid vehicles also rely on high voltage batteries to supply a portion of the propulsion energy and these batteries require rapid warm-up for efficient operation.
Therefore the need exists for a single, integrated unit for both hybrid vehicles and engine-only powered vehicles, which provides supplemental heat for powerplant efficiency, emissions, and customer satisfaction.